1. Field of the Invention
The present invention relates to the field of liquid crystal displaying, and in particular to a backlight module and a liquid crystal display device using the backlight module.
2. The Related Arts
Liquid crystal displays have a variety of advantages, such as thin device body, low power consumption, and being free of radiation, and are thus widely used. Most of the liquid crystal displays that are currently available in the market are backlighting liquid crystal displays, which comprise a liquid crystal display panel and a backlight module. The operation principle of the liquid crystal display panel is that, with liquid crystal molecules interposed between two parallel glass substrates, a number of tiny vertical and horizontal electrical wires are arranged between the two glass substrates to selectively receive application of electricity thereto to control the rotation direction of the liquid crystal molecules in order to refract out light emitting from the backlight module for generating images. Since the liquid crystal display panel itself does not emit light, light must be provided by the backlight module in order to normally display images. Thus, the backlight module is one of the key components of a liquid crystal display. The backlight modules can be classified in two types, namely a side-edge backlight module and a direct backlight module, according to the position where light gets incident. The direct backlight module comprises a light source, such as a cold cathode fluorescent lamp (CCFL) or a light-emitting diode (LED), which is arranged at the backside of the liquid crystal display panel to form a planar light source directly supplied to the liquid crystal display panel. The side-edge backlight module comprises an LED light bar, serving as a backlight source, which is arranged at an edge of a backplane to be located rearward of one side of the liquid crystal panel. The LED light bar emits light that enters a light guide plate (LGP) through a light incident face at one side of the light guide plate and is projected out of a light emergence face of the light guide plate, after being reflected and diffused, to pass through an optic film assembly to form a planar light source for the liquid crystal panel.
Referring to FIG. 1, a schematic view is given to show the structure of a conventional liquid crystal display device. In the structure, the backlight module has a backlight source 100 that is directly mounted to a bottom plate 302 of a backplane by means of screwing of bolts. The backlight source 100 comprises a printed circuit board (PCB) 102 in which stepped-configuration holes 120 are formed. Heads of bolts 150 are respectively and completely received in the stepped-configuration holes 120 so that the top surface of the PCB 102 is kept regular and flat. A reflector plate 1500 is directly positioned on the PCB 102 so that an arrangement of a supporting structure is not necessary thereby lowering down the cost and at the same time reducing the thickness of the liquid crystal display device.
However, since the PCB 102 has a limited thickness, forming the stepped-configuration holes 120 in the PCB 102 may lead to deterioration of the strength of the PCB 102 so that the bolts 150 that are arranged in the PCB 102 may not securely fix the PCB 102 on the bottom plate 302 of the backplane and thus the quality of the liquid crystal display device is deteriorated.